1. Field of the Invention
The present invention relates to a generator motor for vehicles that is mounted on a vehicle and functions as a generator or a motor.
2. Description of the Related Art
Conventionally, it is known that one generator motor in a vehicle drives vehicle-mounted devices and as well performs such functions as generating power for battery charging at the time of engine start and idling stop. When a magnetic field rotor with a magnetic field coil wound around pole cores having claw magnetic poles is used in this generator motor for vehicles, there is known a technique for mounting permanent magnets between the claw magnetic poles neighboring one another along the periphery of the pole cores. The permanent magnets are polarized in a direction opposite to the direction of leakage flux between claw magnetic poles to reduce the leakage fluxes between the claw magnetic poles or relax magnetic saturation due to the magnetic field main magnetic flux. Magnetic fluxes are interlinked with a stator core to increase effective magnetic flux which contributes to power generation or torque generation, whereby output of the generator and the motor is improved.
As an AC generator using permanent magnets, for example, JP-A-10-4661 (page 2, FIGS. 1 to 3) discloses an AC generator that includes a magnetic field coil for exciting a core of a rotor, plural magnets disposed in the core independent from one another, and magnet holding members that connect the plural magnets and are mounted together with the magnets. A molded product made from a nonmagnetic substance, resin, or the like is used as the magnet holding members.
Improvement of generated torque is desired in a generator motor for vehicles. In particular, in a generator motor for vehicles for providing an idle stop function, it is necessary to increase generated torque for engine start, that is, starting torque for a motor. In addition, recently, in the generator motor for vehicles, it is also necessary to increase output of power generation because of the increase in the number of electric devices mounted on a vehicle. In a generator motor having permanent magnets in a rotor, generated torque and amount of power generation increase if the volume of the permanent magnets (magnet power) is increased. However, the permanent magnets are expensive and it is likely that centrifugal force in high-speed rotation of the rotor increases and the permanent magnets scatter when the volume of the permanent magnets increase. Thus, it is desirable that output is improved without increasing the volume of the permanent magnets.
In the conventional technique described above, since the plural permanent magnets are connected and held by holding members to be mounted among the claw magnetic poles, there is the advantage that workability in mounting the permanent magnets is improved and the permanent magnets can be held surely. However, since the permanent magnets are closely mounted in magnet holding sections of the holding members provided among the claw magnetic poles, there is no room for trying new arrangements of the permanent magnets. In addition, since there is no space between the claw magnetic poles and the permanent magnets, it is likely that problems occur because stress is caused by temperature changes due to the difference in thermal expansion of the claw magnetic poles and of the permanent magnets.